sdf: add DOS file formats by searching for format by size as last res…

…ort.

Most disc formats are reconised by finding bytes within the file system
layout on the disc that match a table of geometries in this module.
There are some DOS and Hybrid ADFS+DOS formats where this is not
possible which were recognised by size in disc.c prior to the
introduction of SDF.  This commit re-instates that, via table, but only
when no other format has matched.

src/sdf.c

@@ -52,6 +52,7 @@ static const geometry_t adfs_new_formats[] = {
 };
 
 static const geometry_t adfs_old_formats[] = {
+    { "ADFS+DOS",     SIDES_INTERLEAVED, DENS_DOUBLE, 2720, 80, 16,  256 },
     { "Acorn ADFS L", SIDES_INTERLEAVED, DENS_DOUBLE, 2560, 80, 16,  256 },
     { "Acorn ADFS M", SIDES_SINGLE,      DENS_DOUBLE, 1280, 80, 16,  256 },
     { "Acorn ADFS S", SIDES_SINGLE,      DENS_DOUBLE,  640, 40, 16,  256 },
@@ -82,6 +83,16 @@ static const geometry_t dfs_formats[] = {
     { NULL,                SIDES_NA,          DENS_NA,       0,  0,  0,   0 }
 };
 
+static const geometry_t other_formats[] = {
+    { "ADFS+DOS 800K",     SIDES_INTERLEAVED, DENS_DOUBLE,  800, 80,  5, 1024 },
+    { "ADFS+DOS 640K",     SIDES_INTERLEAVED, DENS_DOUBLE, 2560, 80, 16,  256 },
+    { "DOS 720K",          SIDES_INTERLEAVED, DENS_DOUBLE, 1440, 80,  9,  512 },
+    { "DOS 360K",          SIDES_INTERLEAVED, DENS_DOUBLE,  720, 40,  9,  512 },
+    { "Acorn DFS",         SIDES_SINGLE,      DENS_SINGLE,  800, 80, 10,  256 },
+    { "Acorn DFS",         SIDES_INTERLEAVED, DENS_SINGLE, 1600, 80, 10,  256 },
+    { NULL,                SIDES_NA,          DENS_NA,        0,  0,  0,    0 }    
+};
+
 static int check_id(FILE *fp, long posn, const char *id) {
     int ch;
 
@@ -114,6 +125,7 @@ static const geometry_t *try_adfs_old(FILE *fp) {
     if (check_id(fp, 0x201, "Hugo") && check_id(fp, 0x6fb, "Hugo")) {
         fseek(fp, 0xfc, SEEK_SET);
         sects = getc(fp) | (getc(fp) << 8) | (getc(fp) << 16);
+        log_debug("sdf: found old ADFS signature, sects=%u", sects);
         for (ptr = adfs_old_formats; ptr->name; ptr++)
             if (sects == ptr->size_in_sectors)
                 return ptr;
@@ -146,6 +158,18 @@ static const geometry_t *try_dfs(FILE *fp, uint32_t offset) {
     return NULL;
 }
 
+static const geometry_t *try_others(FILE *fp) {
+    off_t size;
+    const geometry_t *ptr;
+
+    fseek(fp, 0, SEEK_END);
+    size = ftell(fp);
+    for (ptr = other_formats; ptr->name; ptr++)
+        if ((ptr->size_in_sectors * ptr->sector_size) == size)
+            return ptr;
+    return NULL;
+}
+
 static void info_msg(int drive, const char *fn, const geometry_t *geo) {
     const char *sides;
     const char *dens;
@@ -495,9 +519,11 @@ void sdf_load(int drive, const char *fn) {
         if ((geo = try_adfs_old(fp)) == NULL) {
             if ((geo = try_dfs(fp, 0x106)) == NULL) {
                 if ((geo = try_dfs(fp, 0x1001)) == NULL) {
-                    log_error("Unable to determine geometry for %s", fn);
-                    fclose(fp);
-                    return;
+                    if ((geo = try_others(fp)) == NULL) {
+                        log_error("Unable to determine geometry for %s", fn);
+                        fclose(fp);
+                        return;
+                    }
                 }
             }
         }